Segmented rolls



July 17, 1956 A. w. GARDNER 2,754,734

- SEGMENTED ROLLS Filed Jan. 5, 1953 4 Sheets-Sheet 1 INVENTOR A DEYLWADE GAR mus/e A ORNEYS A- w. GARDNER 2,754,734

SEGMENTED ROLLS 4 Sheets-Sheet 2 July 17, 1956 Filed Jan. 5, 1955INVENTOR Anew. WADEG-ARDNE MM ATTORNEYS July 17, 1956 A. w. GARDNER2,754,734

SEGMENTED ROLLS Filed Jan. 5, 1953 4 Sheets-Sheet 5 z 2 =ZZ2 0.15 6-62PAD BEEA DTH Q g UNIT PRESSURE --2 a 2.0 PAD# Z .PAD#2 2 2 x 7 1 0 Q NINVENTOR Anew. WADE GAEDNE'E) ATTORNEY.

July 17, 1956 A. w. GARDNER SEGMENTED ROLLS 4 Sheets-Sheet 4 Filed Jan.5, 1953 INVENTOR ;!6 w QM TTORNEYS United States Patent SEGMENTED ROLLSAdryl W. Gardner, Redlands, Calif.

Application January 5, 1953, Serial No. 329,666

8 Claims. (Cl. 94-50) This invention is a novel roll for compactingloose materials, the roll in effect comprising a cylinder Whose surfaceis partially cut away in a certain pattern so as to leave portions ofthe original cylindrical surface, these portions being in the form ofindividual compaction pads. This novel roll obviates certaindisadvantages inherent in the conventional cylindrical roll and certainother disadvantages inherent in the so-called sheepsfoot roll. Thepresent application is a continuation-in-part of my copendingapplication Serial No. 168,959, filed June 19, 1950.

It is well known that the conventional cylinder when operated as acompaction roll has a high degree of buoyancy with respect to thematerial upon which it is rolling, since its surface contact isrelatively large. This surface contact includes an area under the rollequal to the width thereof times the length of the peripheral arc ofcontact of the roll with the material. However, the continuity ofcontact of the cylinder across the whole width of the roll gives rise toa serious practical disadvantage, i. e. as the roll travels along, itbuilds up a moving wave or wedge of loose material just ahead of itspath. This wedge is pushed ahead of the roll and constantly increases insize until one of several undesirable conditions results. The wedge maybecome so large that the machine is stalled, or the roll may manage toclimb over the wedge and leave behind a large, poorlypacked defect. Thisclimbing effect occurs rather regularly and not only leaves a series ofdefects which must be specially corrected but, in addition,redistributes the materials to various uneven depths causing undesirablealternate thick and thin areas. Obviously, if the machine must climbover such a wedge every few yards, it must have a reserve of horse-powernot used during the regular rolling function but necessary to climb suchdefects. Therefore, the horse-power of the prime mover of the machinemust be chosen in a wasteful manner to provide for these surgerequirements. Moreover, some of the Wedge material escapes at the outeredges of the cylinder and leaves longitudinal ridges along each end ofthe roll.

It is, therefore, one of the principal objects of this invention toobviate this transverse-wedge and longitudinalridge creating tendencywith a minimum impairment of the buoyancy of the roll. These undesirableeffects may be eliminated by providing transversely disposed gaps acrossthe face of the roll at regular intervals so that the material in thewedge is by-passed and left behind in small quantities which may beeasily rolled flat on subsequent passes, the quantities being so smallas to be negligible instead of being allowed to build up toobjectionable size.

However, if the transversely disposed gaps were to be extended the fullwidth of the roll, the total instantaneous roll area pressed against thecontact surface of the material would vary as the gaps passed thematerial. This effect would result in non-uniform buoyancy of the rolland therefore non-uniform material compaction.

2,754,734 Patented July 17, 1956 In order to correct this undesirablenon-uniformity, this invention provides for the division of the rollinto annular rows of compaction pads wherein the gaps of adjacent rowsare staggered. With these gaps correctly located, the total pad areapressing against the arc of contact with the material, when totaledacross the width of the roll, will remain constant as the rollprogresses during any particular pass and therefore the weight of theroll will be supported by the same number of square inches of pad areain contact with the material to be compacted. Thus all of the materialencountered by the pads is compacted to the same degree since the unitforce acting on each unit area is a constant as the roll rotates overthe material. Such a roll has constant buoyancy and can therefore createa smooth finished surface after successive passes. Accordingly, it is avery important object of my invention to provide a roll having aconstant buoyancy as it passes over the material being compacted.

My roll, therefore, has the advantage of a true-cylinder roll (i. e.constant buoyancy), but obviates the disadvantage of a cylindrical roll(i. e. the disadvantage of building up a wedge or ridge of loosematerial resulting in a lumpy finished surface, or in stalling).

As opposed to the cylindrical roll, the sheepsfoot roll is not asurface-finishing roller, and is therefore only of advantage in theearly stages of compaction since it would have a destructive tendency ifused on a finished surface. Its principal advantage over thesolid-cylinder roll lies in its greater unit-area compaction pressure.However, in acquiring this advantage it suffers several very seriousdisadvantages which limit its usefulness to the earlier processingstages.

Basically, the difference between the smooth-faced roll and thesheepsfoot roll is founded on the concept of buoyancy. Since thecylinder is a buoyant roll, it compacts the material from the top down;that is, on successive passes the material is pressed downwardly toprogressively approach the ultimate level of the finished surface. Asopposed to the cylindrical roll, the sheepsfoot roll is non-buoyantbecause its area of contact with the material is relatively very smalland is not a constant as it rotates thereon. It compacts the materialfrom below the ultimate finish level up toward it, that is, theindividual lugs on the sheepsfoot punch through the material instead ofrolling on top of it. The result of this characteristic is that itcannot be used for finish work since it is inherently non-buoyant and,in addition, has a strong tendency to cause fiutfing or loosening of thesurface material and partial destruction of the surface being compacted.

Thus, the sheepsfoot roll, although capable of improving an uncompactedmass of material, is also capable of destroying an already compactedsurface. It is, therefore, an important object of my segmented roll toavoid the destructive tendency of the sheepsfoot roll while retaining aportion of the advanatge thereof. That is, my roll provides increasedunit-area pressure while at the sametime retaining buoyancy.

Moreover, because of the above destructive tendency, the sheepsfoot rolldoes not lend itself to the forming of an elficient compatible tandemcombination when mounted on a machine with a smooth-faced cylindricalroll since the sheepsfoot roll would tend to destroy the finishingeffect of the cylindrical roll. It is accordingly a very importantobject of my invention to provide a roll of the buoyant type which canbe used in a compatible tandem combination with a cylindrical roll toprovide a rolling machine of very versatile character, one which iseflicient not only in the beginning stage of compaction but also in thefinishing stages of surface rolling.

Another important object of my invention is to provide a buoyant typeroll wherein the pads of the respective rows are staggered in such a waythat the leading and trailing edges of the pads in contact with thematerial are not at all in alignment. This is, the transverse edges ofthe pads in one row lie opposite central portions of the pads in anotherrow. An example of the type of structure to be avoided is shown inPatent #243,463, June 28, 188i, to Schaeffer. In Figs. 2 and 3 of thispatent, the leading edges of the pads in one row are axially alignedwith the trailing edges of the pads in the adjacent row so that thealigned transverse shearing edges of the pads on which the roll isresting all contact the material at the same instant. Thus the padscontact the material alternately instead of successively. Such astructure tends to be non-buoyant since the material will shearforwardly of the leading edge of one pad and rearwardly of the trailingedge of the adjacent pad, thereby permitting the pads to sink deeperinto the material in this position than they would sink in a positionwherein the roll was supported on central portions of the pads. In theabove patent such alignment of the pad edges makes no difference sinceSchaeffer was concerned only with traction and not with providing anefiicient surface finishing roll.

Still another object of my invention is to provide a roll capable ofmuch heavier loading than has heretofore been attempted. For example, inbuilding air fields, it is becoming increasingly difiicult to roll thelanding strips to sufficient load-bearing capacity for the enormousweight of the aircraft. The solid cylinder roll when loaded heavilyenough to do the jab can not be moved with any reasonable amount ofpower. Moreover, as soon as it built up a wedge ahead of it, it would bestalled. Conversely, the sheepsfoot roll, it loaded sufficientlyheavily, would simply sink to its hub. My segmented roll, however,builds up no wedge ahead of it and therefore will not stall. Moreover,the pads have enough area so that they can float on the material underthem and continue the processing thereof until a really high loadbearingcapacity surface is produced. In addition, since my roll is notdestructive of finished surfaces, it can be used efficiently from theinitial to the final stages of compacti-on.

Other objects and advantages of my invention will become apparent duringthe following discussion of the accompanying drawings, wherein:

Figure l is an end elevation of my segmented roll assembly showing thearrangement of one row of pads.

Fig. 2 is a front elevation of the roll shown in Fig. 1.

Fig. 3 is a lateral section through a composite steering roll showingthe latter divided into independent right and left sections tofacilitate steering; and showing a complete roll construction includinghub, axle, bearings, spokes, rings, and pads-all carried on aconventional steering yoke.

Fig. 4 shows the compacting pattern left in material being processed bythe roll shown in Fig. 3, the pattern representing one revolutionthereof.

Fig. 5 is a schematic representation in a vertical, axially disposedplace showing lines of constant compaction stress below two pads, theleft pad being half the width of the right pad but loaded to the sametotal weight.

Fig. 6 is a side elevation of a tandem rolling machine wherein thesegmented roll as shown in Fig. 3 is mounted as a guide roll incompatible combination with a conventional cylindrical drive roll.

Fig. 7 is a side elevation of a tandem rolling machine similar to Fig.6, but said machine having a segmented roll on both axles.

Fig. 8 is a schematic representation in a plane normal to the axis ofthe roll showing the dimension of the pads in a row, the spacingtherebetween and the forces acting on the roll.

Fig. 9 is a schematic representation in perspective showing thedimensions and spacings of the pads on a roll having five rows thereof.

In the practical embodiment shown in the drawings, Figs. 1, 2 and 3, thesegmented roll is journaled on an axle 1 which may be supported at itsouter ends by a steering yoke 2 if the roll is used on a machine as aguide roll, though it may also be used as a drive roll, Fig. 7. The hubs3 are journaled in bearings 4 on the axle 1 and carry the supportingmembers for the compaction pads 5. In the embodiment herein illustrated,the pads 5 are fixed around axially spaced annular rings 6 maintained inproper separation by spacers '7. The rings 6 may be supported by aplurality of spokes S radiating from the hubs 3, and additional strengthmay be provided by a disposing some of the spokes at an acute angle withrespect to the axle 1.

This assembly for mounting the compaction pads 5 may be varied in anyexpedient manner so long as the pads 5 are rigidly supported in theirintended positions. In a guide roll assembly as shown in Fig. 3, theroll may be divided into independently journaled halves, but in a driveroll, such division would probably not be of advantage.

One important feature of any pad mounting assembly, however, is that itshould provide an open-work structure which will not collect and retainquantities of the material being processed, otherwise such materialmight pack solidly into the pad interstices and cause the segmented rollto take on the characteristics of a conventional roll to take on thecharacteristics of a conventional cylinder, which result would be highlyundesirable. In the present assembly the open spaces between the padsare not blocked from the inside and therefore any material tending topack therein will be pushed through the outer periphery of the rollinstead of being packed solidly into the interstices.

Fig. 6 shows the roll and yoke assembly of Fig. 3 mounted as the guideroll of a conventional two-axle tandem machine 10, the drive roll 11 ofwhich may be a conventional cylindrical roll. By reference to the groundpattern of the segmented roll, shown in Fig. 4, it may be seen that onthe first pass of the segmented roll, a series of waffie-likedepressions 15 are made by the pads 5, the distance from x-y to xyrepresenting the ground pattern created by one revolution of the roll.After such a pattern has been created by the segmented roll, thematerial at the interstices 16 will, of course, project above thecompacted material 15 so that as the smooth-faced roll 11 follows thepath of the segmented roll, the roll 11 will pass over the raisedmaterial 16 and compact it substantially to the level of the material15. It is very important to note when compacting with a tandemcombination of this type that until the material 16 is compacted levelwith the material 15, by the, smooth-faced roll 11, the roll 11 will actlike a segmented roll whose surface is cut away in a patterncomplementary to the leading segmented roll on the machine, since theraised material 16 initially supports the roll 11 at it passesthereover. Once the material 16 is level with'the material 15, however,the roll 11 will assume again the compaction characteristics of asmooth-faced roll, and will accordingly leave behind it a smoothedsurface. Because of the fact that the segmented roll does not build up atraveling wedge of loose material ahead of it, a machine equipped with aleading roll of this type may be used to process material so looselypacked that it would stall the machine if its leading roll were aconventional cylinder. Accordingly, the segmented roll may be loadedsufiiciently heavily to highly compact the material 15 under the pads 5without stalling, and the cylindrical roll 11, if more heavily loadedthan the segmented roll, will subsequently not only compact the material16 to. the same level as the material 15 but will also deliver a finalstressing to both materials 15 and 16, thus resulting in a relativelysmooth surface after each pass of the machine.

Moreover, compatible tandem combinations are not limited to two-axlemachines. Three-axle tandem machines may be fitted with one or more ofthe segmented rolls to replace the conventional cylindrical rollsgenerally used thereon. Also Where it is necessary to roll very looselypacked material or to roll harder packed material to extremely highdensity, a tandem roller employing a segmented roll on each axle wouldprove to be highly effective, this combination being illustrated in Fig.7.

Thus far, this disclosure has been directed toward the generalcharacteristics and advantages of the segmented roll per se and of thecombinations thereof in tandem rolling machines, without particularemphasis on the size of the pads or the spacing therebetween.

The characteristics of the segmented roll may be explained by referenceto a concept designated as the pressure bulb in Taylors Fundamentals ofSoil Mechanics, page 567 (John Wiley & Sons, 1948), and illustrated inthe present drawings, Fig. 5. The following discussion is intended to betaken only in a qualitative sense and is offered only for the purpose ofshowing that other factors being the same, an increase in pad areabrings with it an increase in the effective depth of compaction of thesoil therebelow. The following example illustrates the effect of merelydoubling the width of the pads on a particular segmented roll withoutchanging the total Weight supported by the roll, and without change inthe other variable factors.

Fig. 5 shows two pressure bulbs, one twice as large as the other, butotherwise identical. At the top of each bulb is the cross section of acompaction pad, the two pads in this figure representing the pads on twodifferent compaction rolls, which pads are assumed to be of the sameannular length. However, pad #1 is only half as wide as pad #2. In orderto provide a clear analogy, it is assumed that each pad supports thesame total weight so that the pressure q per unit area is twice as greatunder pad #1 as under pad #2. The plane of these pressure bulbs isvertical and includes the axis of the rolls. The bulb-shaped lines arelines of constant stress in the material caused by loading of thematerial by the pads pressing downwardly thereon. The unit areapressures are expressed in terms of the magnitudes of qr and qz. If anarbitrary point P1 is chosen below pad #1 and a point P2 of the samedepth is chosen below pad #2, it will be apparent that the stress at P2is .35qz, and that the stress at P1 is .1q1. As stated above, q1=2qz andtherefore, by simple substitution, it is apparent that the radio ofstresses at the chosen depth below the respective pads is:

Thus, doubling the pad width while retaining the same total weightthereon raises the compaction stress by a ratio of 7:4 at the particulardepth chosen in this example.

The reason for this increase in compaction stress below the pad iseasily explained in terms of the shearing motion of material beingcompacted therebelow. It is well known that if a very small bearingsurface is used to compact loose material, in pressing the materialdownwardly it forces a high proportion of the material laterallyoutwardly instead of compacting it downwardly. Before material can becompacted it must be confined to prevent it from retreating from thecompacting force by escaping it laterally. Thus where a larger bearingarea is employed, the material under the center of such area isprevented from escaping laterally by the immediately adjacent materialwhich is also stressed by the bearing area and is opposing such escapewith its own laterally directed force. The result is that the materialnearer the center of the bearing area can not escape and is thussubjected to the full force of compaction.

From the above it appears that two advantages accrue from making thepads 5 relatively large: 1) the material under the larger pad may bestressed to a greater depth than that under the smaller pad and (2)since the volume of material under the larger pad is greater, when unitpressures are equal more material is processed to a greater depth on asingle pass of the pad than would be processed under the smaller pad.

There are, however, other factors which must be considered indetermining pad dimensions and spacings. If the wedge-pushing effect ofthe solid cylindrical roll is to be avoided, annular gaps A must beprovided between the pads in a row. Moreover, since the segmented rollcan be heavily loaded without the danger of stalling inherent in thecylindrical roll, higher unit-area pressures may be used, and thereforeit is useful to provide transverse gaps T between the respective rows ofpads 5 to reduce the total contact area. In view of the pressure bulbdiscussion above, it might seem better to reduce the gaps T and increasethe loading on the roll by making the machine heavier, but practicalconsderations dictate otherwise. In the first place, segmented rollswill be used on many presently existing machines, the weight of which isalready determined. In the second place, the segmented roll will oftenbe used in tandem combination with smooth faced rolls, and since thegaps T leave uncompacted material 16 as shown in Fig. 4, the smoothfaced roll during a pass will resemble a segmented roll of complementarysurface with respect to the segmented roll since the cylindrical rollcompacts the raised portions 16 of the wafiie-like pattern, Fig. 4, asdiscussed above. Therefore the gaps should be wide enough so that thepressure bulbs of adjacent pads do not unduly overlap below the surfacewhereby the said complementary surfaces of the smooth roll will do theirshare of the compaction.

The optimum pad width is thus a compromise between providing a wide padto take maximum advantage of the pressure bulb theory above, andproviding a pad narrow enough to secure sufficient unit-area loading fora given type and weight of machine, and to provide a composite rollhaving pads of such proportion with respect to the cut away area thatsuch rolls may be efficiently used in tandem combinations withsmooth-faced cylindrical rolls. The best compromise Will vary with thecharacter of the different materials being rolled, i. e., soil, asphalt,gravel, etc.

In the design of a particular roll the diagram shown in Fig. 8 is ofassistance. In this figure, a roll of circumference C engages the groundalong an arc of contact S which are subtends an angle 0 at the axis ofthe roll. This roll has compaction pads of length L which pads areannularly spaced by a distance A, the roll of weight W being pulledforward by a force P. The coefficient of rolling friction of the roll isfr=%=tan 0 Values for fr can be found tabulated in standard handbooksfor various types of materials to be compacted. The range in roadconstruction work usually varies between about .5 for loose sand andabout .1 for asphalt. In designing a roll, the largest value of fr whichthe roll is to encounter is chosen and also the diameter of the rollselected. In addition, the number of rows of pads, or multiples thereof,must be determined. Fig. 9 shows a 5 row roll having pads arranged forconstant buoyancy, which arrangement is defined by the formula where Nis the number of rolls, or multiples thereof. Having selected fr, S canbe determined by finding the angle for which fr is the tangent, and thenusing the formula The spacing A between the adjacent pads in a row is Lnl If these formulas are used a constant buoyancy roll will result. Notethat by varying the diameter of the roll and the number of rows in theroll, the arcuate pad length L can be varied.

It is usually desirable to confine L within the range of 6" to 17 inrolls used in road construction since if L goes much below 6", the rollWill start punching through the material and will suffer thedisadvantages of a sheepsfoot roll, i. e., insufficient buoyancy in allmaterials. On the other hand, if the dimension L goes much above 17 thewedge material built up by the pads is dumped, or bypassed, tooinfrequently and the roll will suffer the Wedge-pushing disadvantage ofthe smoothfaced roll.

For general soil and road material compaction work the spacing betweenpads in adjacent rows must be chosen so as to provide pads having awidth which will give a satisfactory pressure bulb profile. In addition,the transverse gaps T must be great enough to prevent undue overlappingof the adjacent profiles below the surface being rolled. For generalroad construction purposes, a satisfactory range of total pacl area tototal area of the cylinder is A to i. e., the cut away area, spacings Aplus spacings T, amounts to M1 to /s of the total cylindrical areadepending on the type of material to be rolled. The above ratio /3 toapplies to rolls of diameters ranging from 36 inches to 72 inches,approximately.

Generally, in rolling non-cohesive or granular materials or in rollingthin lifts, the spacings T need not be great since the profile lines ofthe pressure bulb tend to extend only a short distance outwardly beyondthe sides of the pads; but in rolling cohesive materials or relativethick lifts, the profile lines extend outwardly a considerable distancebeyond the sides of the pads and would unduly overlap if the adjacentrows of pads were not spaced apart further than those used on granularmaterials or thin lifts.

During a rolling operation, the whole pad width will be in contact withthe material at one time, but this is not necessarily true of thearcuate length of the pad. In rolling soft or uncompacted materials theroll will tend to sink thereinto so that a pad at the lower periphery ofthe roll may contact the material over its whole length. But in rollinghard or more compacted materials the length of the contact arc of thepad with the material may be shorter than the full length of the padsince the pad will sink less deeply thereinto. As a matter of fact, bothconditions usually occur during the same processing operation, i. e.,the arc of contact shortens with each pass of the roll.

According to Taylors Fundamentals of Soil Mechanics, the narrowerdimension of a bearing surface controls the amount of force which can beapplied to the column of material below it before shearing will result.Thus, the narrower pad dimension controls the characteristic of thepresent pad, at least in the earlier stages of compaction. This controlby the narrower dimension results from the fact that if shearing takesplace it will be transversely of the longer dimension since a longnarrow bearing surface will tend to cause the material thereunder toshear transversely outwardly thereby permitting the material directlythereunder to escape the pressure. Therefore, so long as the annular arcof contact with the material is longer than the pad width, the pressurebulb will remain unchanged. On successive passes of the roll, however,the length of the arc of contact decreases until eventually its lengthwill equal or be less than the pad width. It should be noted here thatin the case of a solid cylindrical roll, the pressure bulb shrinks onevery pass thereof, since the bulb is controlled by the arc of contactrather than by the roll width, the former being the smaller dimension.In the case of the solid cylindrical roll, this decrease in bulb size isa disadvantage, but in the case of the segmented roll the decrease inthe length of the arc of contact with increase in the material densityis an advantage (until it decreases to the point at which it is lessthan the pad width) because the unit pressure of the roll increases witheach pass without decrease in the depth of the pressure bulb. But anydecrease below the width of the pad is a disadvantage because theprofile of the pressure bulb then becomes dependent on the now-shorterlength of contact dimension and therefore the pressure-bulb shrinks insize on each pass.

The arcuate-length dimension of the pads must be chosen short enough sothat the latter does not build up wedges of objectionable size butleaves behind the wedge material at frequent intervals. On the otherhand, since the pads must have sufficient area to prevent their sinkingtoo deeply into the material being processed during the early stages ofcompaction, the pads must be long enough in comparison to their width togive the buoyancy needed.

Proper choosing of the pad dimensions and spacings will depend on thetype of machine on which the roll is to be mounted and on the characterand density of the material to be processed. Moreover, the pads need notbe rectangular, but may be elliptical or circular, or of other polygonalform. In the drawings the pads are shown to be chamfered somewhat torelieve the tendence of 'the material to shear along the edges of thepads, and to reduce the tendency of the pressure bulbs of adjacent padsto overlap. This chamfer is only about 12 degrees with respect to theworking surface of the pads, and in fact need not be used at all. Thechamfer could also be replaced by a radius of about the same shape.

I claim:

1. A roll for compacting loose material comprising a compositecylindrical broken surface supported on a hub, said surface comprisingspaced adjacent annular rows of substantially similar discretecompaction pads, the pads in each row being separated circumferentiallyby uniform gaps thercbetween and the pads of the rows being mutuallystaggered, said roll including a group of at least three adjacent rowswherein no transverse line drawn across said composite surface parallelwith the axis of the roll passes through more than one gap.

2. A roll as defined in claim I, wherein the total pad area in alltransverse roll sectors of equal angular extent is constant.

3. A roll asdefined in claim 1, wherein the circumferential length ofsaid gaps conforms to the formula wherein A is the gap length, L is thecircumferential pad length, and n is the number of rows in said group.

4. A roll as defined in claim 1, wherein the total pad area of the rollfalls within the range of from /s to /1 the peripheral surface area of asolid cylindrical roll of the same dimensionsas said composite roll.

5. A roll as defined in claim 1, wherein the length of each pad isgreater than its width.

6. A multiple-axle rolling machine having a plurality of axle-mountedcompaction rolls, at least one of said rolls comprising a compositecylindrical broken surface supported on a hub, said surface comprisingspaced adjacent annular rows of substantially similar discretecompaction pads, the pads in each row being separated circumferentiallyby uniform gaps therebetween and the pads of the rows being mutuallystaggered, said roll including a group of at least three adjacent rowswherein no transverse line drawn across said composite surface parallelwith the axis of the roll passes through more than one gap.

7. A machine as defined in claim 6, wherein at least one other of saidrolls is a conventional cylindrical roll.

8. A machine as defined in claim 6, wherein the total pad area in alltransverse roll sectors of equal angular extent is constant.

References Cited in the file of this patent UNITED STATES PATENTS

